79 gauge problem (beyond basic)
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Joined: Aug 2006
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79 gauge problem (beyond basic)
I hope someone can help, I have been trying on and off for two years to figure out why my temp and amp gauge do not work? I am determined to fix before the winter is over.
I have checked the following for temp:
- replaced printed circuit card
- checked all gauges are getting power
- Temp gauge does not move even if green wire to sending unit is grounded
- replaced temp gauge
- replaced sending unit
I did notice of the four posts on the back of the temp gauge one is hot, one is ground, one is for sending unit and the fourth when tested with light on ground lights the test light very faintly and sounds the buzzer?
The Amp gauge when grounded moves?
Is it possible these gauges have a common ground or other issue?
Thanks in advance.
I have checked the following for temp:
- replaced printed circuit card
- checked all gauges are getting power
- Temp gauge does not move even if green wire to sending unit is grounded
- replaced temp gauge
- replaced sending unit
I did notice of the four posts on the back of the temp gauge one is hot, one is ground, one is for sending unit and the fourth when tested with light on ground lights the test light very faintly and sounds the buzzer?
The Amp gauge when grounded moves?
Is it possible these gauges have a common ground or other issue?
Thanks in advance.
Last edited by KGKVette; Mar 2, 2009 at 10:44 PM. Reason: hit wrong button
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
The green wire on the temp gauge sensor is open somewhere. With the dash out power on: put a ground wire on the sensor stud on the gauge, the gauge should peg right.
The 79 has a voltmeter not an ammeter. Take a test meter to the back of it to see whats going on, there should be a hot, ground and light on there.
The 79 has a voltmeter not an ammeter. Take a test meter to the back of it to see whats going on, there should be a hot, ground and light on there.
Safety Car
Joined: Nov 2004
Posts: 4,359
Likes: 57
From: Mundelein Illinois
[QUOTE=KGKVette;1569150201]I hope someone can help, I have been trying on and off for two years to figure out why my temp and amp gauge do not work? I am determined to fix before the winter is over.
From this I would be looking at power and ground. I don't think two guages would go bad at the same time but it is possible. I would get a test light and make sure your getting power and ground at the guages. I have seen with the new circuit boards sometimes the guages are not making connection and you have to push the board up and down a few times to make a good connection.
If they are getting power then I would look at the sending wire or guage but your volt meter has no sending unit. You cand hook up power and ground from the battery to check the volt meter.
From this I would be looking at power and ground. I don't think two guages would go bad at the same time but it is possible. I would get a test light and make sure your getting power and ground at the guages. I have seen with the new circuit boards sometimes the guages are not making connection and you have to push the board up and down a few times to make a good connection.
If they are getting power then I would look at the sending wire or guage but your volt meter has no sending unit. You cand hook up power and ground from the battery to check the volt meter.
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Joined: Aug 2006
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Solution
Thank you to everyone who posed a reply. Here is what fixed the problem, might help someone else:
I noticed there was ceramic bridge on both the Battery and Temp gauge. I reversed this piece and noticed a metallic ring around post. As it seems these were installed backwards from previous owner. I used gator clips to attach the gauge directly to the wire harness and all gauge worked. Repeated for Battery, the metal ring on the ceramic piece needs to face up and you need to place a washer on nut to secure and make contact with the post and pace anther nut on top of the printed circuit to complete the circuit.
I never thought this would have been the problem.
I noticed there was ceramic bridge on both the Battery and Temp gauge. I reversed this piece and noticed a metallic ring around post. As it seems these were installed backwards from previous owner. I used gator clips to attach the gauge directly to the wire harness and all gauge worked. Repeated for Battery, the metal ring on the ceramic piece needs to face up and you need to place a washer on nut to secure and make contact with the post and pace anther nut on top of the printed circuit to complete the circuit.
I never thought this would have been the problem.
